Embodiments of the present invention generally relate to flip flops, and more particularly relate to a flip flop having a protection circuit for protecting data stored by the flip flop from radiation impacts.
Unless otherwise indicated herein, the circuits and circuit methods described in the background section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in the background section.
Storage circuits, such as flip flops, latches, and memories, store data in the form of charge. Relatively high energy radiation (“radiation”), such as high energy photons, electrons, protons, neutrons, etc. can disrupt the data stored in storage circuits by disrupting the charge that represents the data. The radiation can free electrons and generate holes in the material (e.g., semiconductor material) storing the charge. The free electrons and holes can change the charge representing the data and therefore can change the state of the data.
Radiation having sufficient energy to change the data in a storage circuit is prevalent in many environments, such as space, high-altitude flight, near nuclear reactors, particle accelerators, and the like. Radiation of such energy also reaches the surface of the Earth, however, with generally less intensity but does cause storage circuits to fail. Radioactive isotopes in circuit-packaging materials have historically been a source of radiation for storage circuits although the potential of radiation from radioactive isotopes in circuit packaging has been reduced in recent years from the use higher purity materials used for circuit packaging.
Storage circuits configured for use in environments where radiation of sufficient energy exists are often “hardened” to the effects of such radiation. Hardening generally referrers to a variety of circuit designs, circuit methods, circuit packaging, and the like configured to mitigate the effects of such radiation. Further, circuits for which low failure rates are desired also hardened. For example, in banking applications were circuits operate substantially continuously for long periods of time may have a high probability of eventually being struck by radiation and possibly having a data failure due to the radiation.
The semiconductor industry continues to strive to design and manufacture new storage circuits and the like, which can withstand the negative effects of radiation on charge that represents data in a storage circuit.